The present invention broadly relates to an improved scrubbing apparatus for extracting contaminating particulate matter entrained in a gas stream employing a liquid washing medium. The principles of the present invention are particularly applicable, but not necessarily restricted to the removal of entrained paint particles from the exhaust air stream from paint spray booths to provide an environmentally acceptable effluent while simultaneously recovering the paint overspray for processing in a paint reclamation system.
A variety of scrubbing devices have heretofore been used or proposed for use in association with paint spray chambers or booths. While such devices have provided satisfactory operation in the past, the imposition of more stringent environmental specifications on the maximum permissible levels of particulate matter in the exhaust effluent has necessitated further development of improved designs to increase the effectiveness of such devices in capturing and extracting large proportions of the entrained particulate matter.
In addition to increasingly stringent particulate matter removal, permissible noise levels for such apparatus are becoming more stringent which tends to conflict with the need to achieve better particulate removal. Another important factor to be considered in the design of such scrubbing apparatus is the need to effectively remove the liquid droplets from the gas stream prior to passage of the gas stream out through the exhaust stack or ductwork. Typically, the scrubbing liquid utilized is water which if allowed to remain in the air stream may result in accelerated corrosion of the exhaust stack.
Additionally because the exhaust stack or ductwork of such apparatus is vented outside of the building housing the scrubbing apparatus, it is important to incorporate in such apparatus means to prevent loss of warm plant air or infiltration of cold outside air during periods when the scrubber is not operating.
Accordingly, the present invention provides an improved scrubber apparatus particularly well suited for use in paint spray booth applications such as those commonly employed for the painting of motor vehicles which overcomes the problems associated with prior designs and achieves an extremely high degree of efficiency at very low noise levels. The scrubber apparatus of the present invention incorporates a pair of spaced constrictions through which the gas stream is serially drawn along with liquid overflow from the flood plates. The constrictions are designed such that the gas stream effects atomization of the liquid as they flow therethrough thus causing a mixing of the particulate matter entrained in the gas stream and the atomized liquid whereby the gas stream is cleansed of the entrained particulate matter. The first of these two constrictions is defined by a baffle member and liquid level contained within a trough which operates to substantially reduce exchange of interior and exterior air when the apparatus is not in use in addition to performing a first level of gas stream scrubbing. The second constriction serves to further scrub the gas stream flowing therethrough so as to assure a very high degree of particulate removal from the gas stream. Additionally, because this second constriction is being conducted by the first constriction, transmission of noise emanating from the second constriction into the spray chamber is substantially reduced. Thus, it is possible to so design the first and second constrictions that the major scrubbing action which typically results in the greatest noise generation is performed by the second constriction thereby maintaining a relatively low noise level within the spray chamber. Additionally, because scrubbing action is being accomplished at both constrictions, a very high level of efficiency in particulate removal from the gas stream is achieved.
The present invention also incorporates an improved arrangement for removal of the liquid from the gas stream prior to discharge to the exhaust stack. A series of baffle members are provided which create a labyrinth requiring the gas stream negotiate a series of 90.degree. and 180.degree. turns in a horizontal plane followed by a vertical baffle requiring the gas stream negotiate an initial turn of 90.degree. followed by a 180.degree. turn both in the vertical plane. This baffle arrangement effectively assures that all liquid droplets are removed from the air stream prior to its reaching the exhaust stack. Additionally, the positioning of the various baffle members has been designed so as to enable relatively easy access to the passages defined thereby so as to greatly facilitate cleaning of the apparatus with a minimum of time being required.
Accordingly, the present invention provides an improved scrubbing apparatus having the ability to achieve very high efficiency in removal of particulate matter at very low noise levels and to effectively remove liquid droplets from the gas stream so as to insure only a dry, clean, gas stream is discharged through the exhaust stack. Additionally, the design is executed so as to greatly facilitate periodic maintenance and cleaning thereof with a minimum amount of time and effort being required.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.